1. Field of the Invention
The present invention relates to compositional buffers composed of a silicate- or borate-based compound that readily forms an amorphous structure, and a method for manufacturing the compositional buffers, as well as to a method for manufacturing electronic ceramics, and more particularly relates to novel compositional buffers and method for manufacturing the same, and a method for manufacturing electronic ceramics using the compositional buffers, with which the surfaces of the fine crystal grains of an electronic ceramic containing highly volatile cations of bismuth, lead, or the like, or a thin film thereof, are covered with the above-mentioned compositional buffer by chemical solution method in the process of synthesizing an electronic ceramic containing a volatile element or a thin film thereof, thereby preventing the loss of components through volatilization, preventing the precipitation of metal at the grain boundary by incorporating any cations that have been added in excess into the amorphous structure, and enabling the electronic ceramic or thin film thereof to be maintained at its stoichiometric composition.
2. Description of the Related Art
In the synthesis of an electronic ceramic or thin film thereof such as a ferroelectric or superconductor of a bismuth-based laminar compound or lead-based perovskite compound containing highly volatile cations such as bismuth or lead, the bismuth, lead, or the like volatilizes in the course of sintering during the synthesis process, which has led to the adoption of methods in which an organometallic salt or an oxide powder containing an excess amount of bismuth, lead, or the like is added ahead of time to the raw material solution or powder, or in which the sintering is performed in an atmosphere saturated with bismuth, lead, or another such volatile element. When an excess amount of a volatile element is thus added externally, the volatile metal element added in excess evaporates away during high-temperature sintering, the result being that an electronic ceramic or thin film thereof that is free of compositional defects can be synthesized.
An electronic ceramic or thin film thereof synthesized by a conventional method is premised on the fact that the volatilization of the volatile element added in excess will be volatilized in the course of the high-temperature sintering performed during the manufacturing process, resulting in the composition being close to the stoichiometric composition. However, while such a method is suitable when the sintering reaction is conducted at high temperature, if the sintering is performed at low temperature, or if there is a change in the sintering time, firing atmosphere, or sample shape, the volatilization rate will vary, so the volatile element may remain behind, or remaining volatile element cations may be reduced and precipitated in the form of a metal. An element that precipitates in the form of a metal diminishes the characteristics of the electronic ceramic or thin film thereof. Therefore, conventional methods were not suited to the synthesis of electronic ceramics or thin films thereof at low temperature.
In light of the above-mentioned prior art, the inventors conducted diligent research aimed at developing a novel synthesis method in which an electronic ceramic containing a volatile element such as bismuth or lead or a thin film thereof is synthesized at low temperature and adjusted to its stoichiometric composition. As a result, they arrived at the present invention upon discovering that if the surfaces of the fine crystal grains that make up an electronic ceramic or thin film thereof are covered by chemical solution method with a silicate- or borate-based compound that readily forms an amorphous structure, loss of composition that would otherwise be caused by volatilization can be prevented, and if cations of a volatile element that has added in excess are incorporated into an amorphous structure, the precipitation of metal at the grain boundary can be prevented, allowing the electronic ceramic or thin film thereof to be maintained at its stoichiometric composition.